Ambient Nitrous Oxide Research Articles

Quantifying changes in ambient nitrous oxide levels with catalytic cracking in the labour ward

Quantifying changes in ambient nitrous oxide levels with catalytic cracking in the labour ward

Implementing nitrous oxide cracking technology in the labour ward to reduce occupational exposure and environmental emissions: a quality improvement study.

Nitrous oxide, a potent greenhouse gas, is a common labour analgesic. One method which may reduce its carbon footprint is to 'crack' the exhaled gas into nitrogen and oxygen using catalytic destruction. In this quality improvement project, based on environmental monitoring and staff feedback, we assessed the impact of nitrous oxide cracking technology in the maternity setting. Mean ambient nitrous oxide levels were recorded during the final 30 minutes of uncomplicated labour in 36 cases and plotted on a run chart. Interventions were implemented in four stages, comprising: stage 1, baseline (12 cases); stage 2, cracking with nitrous oxide delivered and scavenged via a mouthpiece (eight cases); stage 3, cracking with nitrous oxide via a facemask with an air-filled cushion (eight cases); stage 4, cracking with nitrous oxide via a low-profile facemask, and enhanced coaching on the use of the technology (eight cases). The median ambient nitrous oxide levels were 71% lower than baseline in stage 2 and 81% lower in stage 4. Staff feedback was generally positive, though some found the technology to be cumbersome; successful implementation relies on effective staff engagement. Our results indicate that cracking technology can reduce ambient nitrous oxide levels in the obstetric setting, with potential for reductions in environmental impacts and occupational exposure.

An 18 year data-linkage study on the association between air pollution and acute limb ischaemia.

Background: There is limited information regarding the effects of air pollutants, such as nitrogen oxides (NOx), nitric oxide (NO2), nitrous oxide (NO) and particulate matter with a diameter smaller than 10 μm (PM10), on acute limb ischaemia (ALI), a peripheral arterial disease (PAD) often with a poor clinical outcome. Patients and methods: We conducted an 18-year retrospective cohort study using routinely collected healthcare records from Ninewells Hospital, Dundee, and Perth Royal Infirmary, in Tayside, Scotland, UK from 2000 to 2017. ALI hospitalisation events and deaths were linked to daily NOx, NO2, NO and PM10 levels extracted from publicly available data over this same time period. Distributed lag models were used to estimate risk ratios for ALI hospitalisation and for ALI mortality, adjusting for temperature, humidity, day of the week, month and public holiday. Results: 5,608 hospital admissions in 2,697 patients were identified over the study period (mean age 71.2 years, ±11.1). NOx and NO were associated with an increase of ALI hospital admissions on days of exposure to pollutant (p=.018), while PM10 was associated with a cumulative (lag 0-9 days) increase (p=.027) of ALI hospital admissions in our study. There was no increase of ALI mortality associated with pollution levels. Conclusions: ALI hospital admissions were positively associated with ambient NOx and NO on day of high measured pollution levels and a cumulative effect was seen with PM10.

An Exploration of Common Greenhouse Gas Emissions by the Cyanobiont of the Azolla-Nostoc Symbiosis and Clues as to Nod Factors in Cyanobacteria.

Azolla is a genus of aquatic ferns that engages in a unique symbiosis with a cyanobiont that is resistant to cultivation. Azolla spp. are earmarked as a possible candidate to mitigate greenhouse gases, in particular, carbon dioxide. That opinion is underlined here in this paper to show the broader impact of Azolla spp. on greenhouse gas mitigation by revealing the enzyme catalogue in the Nostoc cyanobiont to be a poor contributor to climate change. First, regarding carbon assimilation, it was inferred that the carboxylation activity of the Rubisco enzyme of Azolla plants is able to quench carbon dioxide on par with other C3 plants and fellow aquatic free-floating macrophytes, with the cyanobiont contributing on average ~18% of the carboxylation load. Additionally, the author demonstrates here, using bioinformatics and past literature, that the Nostoc cyanobiont of Azolla does not contain nitric oxide reductase, a key enzyme that emanates nitrous oxide. In fact, all Nostoc species, both symbiotic and nonsymbiotic, are deficient in nitric oxide reductases. Furthermore, the Azolla cyanobiont is negative for methanogenic enzymes that use coenzyme conjugates to emit methane. With the absence of nitrous oxide and methane release, and the potential ability to convert ambient nitrous oxide into nitrogen gas, it is safe to say that the Azolla cyanobiont has a myriad of features that are poor contributors to climate change, which on top of carbon dioxide quenching by the Calvin cycle in Azolla plants, makes it an efficient holistic candidate to be developed as a force for climate change mitigation, especially in irrigated urea-fed rice fields. The author also shows that Nostoc cyanobionts are theoretically capable of Nod factor synthesis, similar to Rhizobia and some Frankia species, which is a new horizon to explore in the future.

Effect of Continuous versus Interrupted Administration of Nitrous Oxide-Oxygen Inhalation on Behavior of Anxious Pediatric Dental Patients: A Pilot Study

The purpose of this study was to determine the effect of interrupted administration of nitrous oxide (N2O) inhalation, after obtaining profound local anesthesia, on the behavior of mild to moderately anxious pediatric patients during routine restorative dentistry. Healthy children, 5 to 8 years old, requiring nitrous oxide/oxygen inhalation sedation and bilateral mandibular restorative treatment performed in two sequential appointments under local anesthesia were recruited for this study. After profoundness of the local anesthesia was confirmed, the subject was randomly assigned to either Protocol A (50% N2O/50% O2) or Protocol B (100% O2) and restorative dental care was completed. On the second appointment, the subject was assigned to the alternate protocol. Hemoglobin oxygen saturation remained constant with no episodes of oxygen desaturation recorded. There were no statistically significant differences (P > .05) in pulse rate or behavior change noted between the two protocols. The implication of this pilot study was significant in consideration of the desire to minimize chronic exposure to ambient nitrous oxide and its potential health hazards to the dental team. These findings challenge the traditional practice of N2O maintenance throughout the dental appointment.

Potential role of Thermus thermophilus and T. oshimai in high rates of nitrous oxide (N2O) production in ∼80 °C hot springs in the US Great Basin

Ambient nitrous oxide (N(2)O) emissions from Great Boiling Spring (GBS) in the US Great Basin depended on temperature, with the highest flux, 67.8 ± 2.6 μmol N(2)O-N m(-2) day(-1) , occurring in the large source pool at 82 °C. This rate of N(2)O production contrasted with negligible production from nearby soils and was similar to rates from soils and sediments impacted with agricultural fertilizers. To investigate the source of N(2)O, a variety of approaches were used to enrich and isolate heterotrophic micro-organisms, and isolates were screened for nitrate reduction ability. Nitrate-respiring isolates were identified by 16S rRNA gene sequencing as Thermus thermophilus (31 isolates) and T. oshimai (three isolates). All isolates reduced nitrate to N(2)O but not to dinitrogen and were unable to grow with N(2)O as a terminal electron acceptor. Representative T. thermophilus and T. oshimai strains contained genes with 96-98% and 93% DNA identity, respectively, to the nitrate reductase catalytic subunit gene (narG) of T. thermophilus HB8. These data implicate T. thermophilus and T. oshimai in high flux of N(2)O in GBS and raise questions about the genetic basis of the incomplete denitrification pathway in these organisms and on the fate of biogenic N(2)O in geothermal environments.

Ambient levels of nitrous oxide in a modular ambulance

Nitrous oxide has been occasionally used as a prehospital analgesic over the last 3 decades. It has been shown to be an effective analgesic agent [1], but concerns have been raised about exposing prehospital personnel to high ambient levels of nitrous oxide within the confines of the ambulance. Historical concerns about possible detrimental effects of long-term exposure to health care workers prompted the National Institute of Occupational Safety and Health (NIOSH) to issue recommendations regarding acceptable levels of nitrous oxide exposure. NIOSH currently recommends a time-weighted average of 25 ppm for staff exposure during administration of nitrous oxide [2]. El Dorado County Emergency Medical Services (EMS), Placerville, Calif, was granted optional scope permission by the California State EMS Authority to use nitrous oxide in the ambulance for analgesia in 1997. In early 2004, we conducted a study to measure ambient nitrous oxide levels in the ambulance. The study assessed compliance with NIOSH standards for acceptable levels of nitrous oxide. Unlike previous studies, we attempted to replicate actual clinical conditions as closely as possible. This meant setting up the modular ambulance environment in a configuration consistent with how paramedics would normally operate. We also designed the study to examine the effect of patient conversation on ambient nitrous oxide levels.

Exposure to nitrous oxide in a paediatric dental unit

The aim of this study was to evaluate the 8-h time-weighted average (8-h TWA) exposure to nitrous oxide of dentists working in a paediatric dental unit, and to relate this to various operator, patient and environmental factors. This prospective, open-label study monitored nitrous oxide levels using either a personal dosimeter or an electronic sensor worn by the operator. Information was recorded by three dental operators administering nitrous oxide/oxygen for inhalational sedation. Thirty-four paediatric dental patients were treated over a total of 17 treatment sessions. Active scavenging was used for all children; 23 were treated using the Porter-Brown scavenging system and 11 with the Accutron system. Exposure to nitrous oxide expressed as an 8-h TWA ranged from 16 to 374 ppm, with a mean of 151 ppm. The recommended 8-h TWA of 100 ppm was achieved in only 38% of cases. Ambient nitrous oxide levels apparently increased with restorative treatment, poorer behaviour, when the extractor fan was switched off, with patients over 10 years of age and an increased number of sequential patients. This study found that the recommended 8-h TWA was achieved in only 38% of treatment episodes, despite the use of active scavenging.

High-volume aspiration as a supplemental scavenging method for reducing ambient nitrous oxide levels in the operatory: a laboratory study.

Occupational exposure to low levels of nitrous oxide (N2O) have been associated with adverse health effects. The National Institute for Occupational Safety and Health has established a threshold guideline of 25 ppm N2O. The purpose of this laboratory study was to determine the effectiveness of a high-volume dental aspirator as a supplemental device to reduce ambient N2O levels in the operatory. The investigation evaluated four experimental groups that were assigned based on whether or not the aspirator was used and on the rate at which operatory ventilation was established (5 or 10 room air exchanges per hour). Ambient N2O levels were monitored at 30 cm from the nasal hood using an infrared spectrophotometer. The room air exchange rate was measured with a flow hood and then manipulated to the desired ventilation rate. N2O levels were detected with a spectrophotometer and data were recorded with a microprocessor that continuously collected data. The results demonstrated that both utilization of supplemental oral aspiration and increased operatory ventilation significantly reduced ambient N2O levels. It was concluded that a high-volume aspirator, when used in conjunction with the normal scavenging system, can significantly reduce ambient N2O levels to within the guidelines established by the National Institute for Occupational Safety and Health.

Ambient nitrous oxide emissions from different landform complexes as affected by simulated rain‐fall

Abstract The Tesponse of ambient nitrous oxide (N2O) emissions to four levels of simulated rainfall (5, 10, 20, and 40 mm) was assessed using large‐diameter cores of undisturbed soil in a greenhouse. The soil cores were taken from the two dominant soil‐landform groups present in the study area: Mollic Albaqualfs in footslope complexes and Typic Haploborolls in shoulder complexes. The footslope complexes had higher ambient N2O emission than the shoulder complexes at all rainfall levels which was attributed to the differences in inherent characteristics of the soils occurring at these landscape positions. This demonstrates the importance of a spatially‐based investigative approach to account for landscape‐scale differences in soil characteristics when investigating N2O emission at a large scale. Rainfall level strongly influenced the aeration status of the soil which, in turn, affected N2O emission. Rainfall showed to be a potential suitable parameter in a predictive model for N2O emissions (R2 = 0.73∗∗ and...

Operatory Ventilation and Scavenger Evacuation Rate Influence on Ambient Nitrous Oxide Levels

Investigations have shown that greater than Federally-recommended levels of ambient nitrous oxide often exist in the dental workplace. The purposes of this investigation were to examine the influences of (1) operatory ventilation rate and (2) scavenger evacuation rate on ambient nitrous oxide concentrations within a closed dental operatory. This laboratory investigation utilized a scavenging nasal mask assembly (Porter/Brown) to deliver 40% nitrous oxide in oxygen, at a total flow rate of 5 L/min, to a mannequin positioned supinely in a dental chair. Eight experimental groups were assigned based on combinations of operatory air exchange rates (0, 5, 10, or 15 room air changes per hour) and scavenger evacuation rates (18.8 L/min and 21.4 L/min). Ambient nitrous oxide levels were monitored at four locations (0, 15.3, 30.7, and 61.4 cm) from the nasal mask by means of an infrared spectrophotometer (Miran 1B). The operatory air exchange rate was measured with a flow hood (Short Ridge) and manipulated to one of the desired ventilation rates. Time-weighted average (TWA) concentrations of ambient nitrous oxide (ppm) were continuously recorded at 15-second intervals with a microprocessor (DL332F Datalogger) connected directly to a microcomputer. The results demonstrated that significantly reduced (p < 0.05) ambient nitrous oxide levels were achieved with increasing room air exchange rates and the high scavenger evacuation rate. It was concluded that operatory ventilation and scavenger evacuation rates were significant control measures available for reduction of ambient nitrous oxide to Federally recommended levels.

Reduction of nitrous oxide contamination in a paediatric hospital.

Ambient nitrous oxide concentrations were recorded in an operating room during delivery of the gas at low and medium flow-rates, with and without the application of simple scavenging devices. Residual background levels of nitrous oxide were still present more than one hour after disconnection of the flowmeters and use of the room. Scavenging reduced concentrations ten-fold. Adjacent corridors and the post-anaesthetic recovery room were contaminated with nitrous oxide from the operating rooms and from patients. A vigorous programme of checking for leaks and repairing and maintaining equipment, coupled with the use of suction scavenging, can reduce atmospheric contamination with nitrous oxide below 30 p.p.m., which is well within the limit suggested by the U.S. National Institute for Occupational Safety and Health.

A Study of Waste Gas Scavenging in Operating Theatres

Measurements of atmospheric nitrous oxide concentrations were made in eight hospitals, using 30 anaesthetic machines and locations, during 41 anaesthetic administrations or simulations. All areas were air conditioned, two by laminar flow devices. All anaesthetic machines and ventilators were fitted with commercially available gas collector (scavenger) valves. In all areas except one, venturi suction was used to exhaust gases. Pollution levels during endotracheal anaesthesia did not exceed the recommended 30 ppm. except where leaking anaesthetic machines or nitrous oxide supplies were used. In two instances where paediatric anaesthesia was administered through uncuffed endotracheal tubes nitrous oxide levels were also excessive. Of nine anaesthetics administered through face masks, only in one was the ambient nitrous oxide concentration acceptable. During induction of anaesthesia using nitrous oxide, unacceptable peaks of concentration were encountered. In two air conditioned recovery rooms tested, nitrous oxide concentration was acceptable. The collector valves performed their function satisfactorily, but laminar flow air conditioning was insufficient in itself to maintain acceptably low nitrous oxide concentration without the use of scavenging.